Textured continuous cleaning surface for cooking ovens

ABSTRACT

A cooking oven having at least the bottom wall and the two sides, and the rear wall, formed of embossed metal with a layer of vitreous porcelain enamel of dark porous matte finish covering the exposed surface of the embossed metal to have the continuous cleaning property during normal cooking operations of diminishing the accumulation of carbonaceous residue which results from the exposure to grease spatters during cooking.

United States Patent 1191 [451 Jan. 8, 1974 TEXTURED CONTINUOUS CLEANING SURFACE FOR COOKING OVENS 12/1970 Lee 126/19 Primary Examiner-Edward G. Favors Attorney-Richard L. Caslin et a].

[57] ABSTRACT A cooking oven having at least the bottom wall and the two sides, and the rear wall, formed of embossed metal with a layer of vitreous porcelain enamel of dark porous matte finish covering the exposed surface of the embossed metal to have the continuous cleaning property during normal cooking operations of diminishing the accumulation of carbonaceous residue which results from the exposure to grease spatters dur- 7 Claims, 4 Drawing Figures [52] U.S. c1 126/19 R [51] Int. Cl M11) 1/00 [58] Field of Search 126/19, 273; 117/129 [56] ReferencosCited UNITED STATES PATENTS mg 3,266,477 8/1966 Stiles. 126/19 mil \YIZZ TEXTURED CONTINUOUS CLEANING SURFACE FOR COOKING OVENS BACKGROUND OF THE INVENTION Late in 1963, the first pyrolytic self-cleaning oven was introduced to the public and it incorporated the teachings of the basic U.S. Pat. No. 3,121,158 of Bohdan Hurko, which is assigned to the same assignee as is the present invention. A pyrolytic self-cleaning oven is one in which the oven. air or oven interior wall surfaces are raised above normal cooking temperatures into a pyrolytic temperature range somewhere between 750F. and 950F. for a sufficient time interval. During such a high temperature cycle, the food soils and grease spatters that accumulate on the interior surfaces of the oven are removed automatically in an oxygen-starved atmosphere by a pyrolytic step with the consequent production of gaseous primary degradation products which are then subjected to further oxidation so as to produce corresponding gaseous secondary degradation products that are substantially completely devoid of carbon monoxide, smoke, odors and vapors, and finally exhausting the gases to the atmosphere.

Several years later, continuous cleaning ovens were introduced incorporating the teachings of U.S. Pat. No. 3,266,477 using a porcelain enamel coating having partially embedded therein a catalyst carrier which in turn supports an oxidizing catalyst which will oxidize the food residues on the interior surface of the walls forming the oven cooking cavity so that at moderate temperatures such as normal cooking temperatures beneath 550F., the oven walls could be gradually cleaned to a limited extent of the carbonaceous residues, without having to raise the temperature above the normal cooking temperatures. Such a catalytic coating incorporated a catalyst selected from the group consisting of ruthenium, palladium, platinum, or oxides, cerates, manganates, manganites, chromates, chromites, or vanadates of cobalt, nickel, cerium, ruthenium, palladium and platinum. Such a catalytic coating also had a dark, porous matte finish. However, it proved to be mostly unsatisfactory because it was often weak in abrasion resistance and of little effectiveness for diminishing and retarding the accumulation of food soils and grease spatters on the oven interior surfaces at oven temperatures from 350 through 550F. Such catalytic coatings seemed to function more as a porous blotter which absorbed the soil, but did not entirely remove it. In other words, by testing the continuous cleaning action by weighing a sample panel with a catalytic coating before and after the cleaning action, there was usually little perceptible change in the weight of the panel after it was heated for a long period of time, although some visual change in the appearance of the panel could be detected by the naked eye. Unfortunately, when the catalytic coating became smothered by the soil, the cleaning action virtually stopped because the catalyst required exposure to the air as a source of oxygen in the oxidation process. When this smothering action occurred, the only remedy was to wash, scrape or scrub the surface manually with a strong cleaning agent, and this is when the catalytic coating would loosen and become separated from the panel.

Many oven manufacturers have adopted the technique of stippling the dark matte porous surface with small, white dots of white enamel dispersed indiscriminately like the stars in the heavens in a camouflage attempt to hide the food stains and render the oven wall surfaces more acceptable over a longer period of use. Another technique which tended to prolong the acceptability of the continuous cleaning coating was the elmination of the oven interior lamp which darkened the oven interior and made it more difficult for a person to determine whether or not food soils were present on the interior surfaces of the oven.

Several improved continuous coatings have been -introduced recently, such as that of U.S. Pat. No. 3,580,733 of Robert Ott which is assigned to the SCM Corporation. This patent teaches a satisfactory continuous cleaning coating for use in the present invention and its teachings are incorporated herein by reference.

The principle object of the present invention is to provide a continuous cleaning surface adhering to an embossed metal substrate so as to create a natural pattern of shadows on the surface and thereby break up the line of sight and reduce specular reflectance therefrom so as to disguise any food soil that might be present thereon.

A further object of the present invention is to provide an embossed metal surface with a continuous cleaning coating so as to increase the surface area of the coating and thereby increase the cleaning action by an amount proportional to the increase in the surface area.

A still further object of the present invention is to provide an embossed metal surface with a continuous cleaning coating where the thickness of the coating is greatest in the valleys, thereby increasing the depth of the porous matte surface and increasing the porcelain blotter capability in the area'where the soil accumulates the most.

SUMMARY OF THE INVENTION The present invention, in accordance with one form thereof, relates to a baking or broiling oven having metal walls forming an oven cooking cavity where certain walls are provided with an embossed surface that is coated with a layer of vitreous porcelain enamel of porous matte finish that adheres to the exposed surface of the embossed metal substrate. This layer has a continuous cleaning property of diminishing any accumulation of carbonaceous residue that becomes lodged on such wall surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS- This invention will be better understood from the following description taken in conjunction with the accompanying drawings, and its scope will be pointed out in the appended claims.

FIG. 1 is a front elevational view of a built-in wall oven with the fold-down door resting in the open position to show the continuous cleaning embossed bottom and vertical side walls of the oven liner of the present invention, it being understood that all of such walls would be embossed.

FIG. 2 is a fragmentary plan view on an enlarged scale of the small portion of the embossed metal substrate for receiving a coating of porcelain enamel with continuous cleaning properties embodying the present invention.

FIG. 3 is a cross sectional elevational view on an enlarged scale through the embossed metal plate of the present invention taken on the line 3-3 of FIG. 2 with a porous enamel layer adhering thereto.

FIG. 4 is another cross sectional elevational view through the embossed metal plate, but taken at right angles to that of FIG. 3 on the line 4-4 of FIG. 2 with the porous enamel applied thereto.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to a consideration of the drawings and, in particular to FIG. I, there is shown only one embodiment of this invention comprising a built-in wall oven having an oven body or cabinet structure 11 in which is assembled a box-like oven liner 13 which has a bottom wall 15, opposing vertical side walls 17 and 18 and a vertical rear wall 20 as well as a top wall that is not visible in this view, but is arranged generally parallel with the bottom wall 15. This oven liner 13 is provided with an open front that is adapted to be closed by a hinged oven door 22 for forming an oven cooking cavity 24. It will be apparent to those skilled in this art that this oven liner 13 would be surrounded with heat insulating material'(not shown) such as fibre glass, or the like, that is located between the oven body 11 and the oven liner 13 so as to retain as much of the heat as possible within the oven cavity.

Heat is supplied to the oven cavity 24 by suitable electrical resistance heating elements, only one of which is shown; namely, a lower bake element 25 located adjacent the bottom wall of the oven liner, which is, of course, standard construction in electric ovens. This bake element 25 is a metal sheathed heating element of standard design which comprises a helical resistance wire extending nearly the entire length thereof, and this helical wire is embedded in an insulating material such as magnesium oxide which is in turn covered with a metal sheath. A standard electricoven would also include an upper broil element (not shown) located adjacent the top wall of the oven liner.

While I have elected to illustrate my invention as it would be embodied in an electric oven, it will be apparent to those skilled in this art that the same invention could be incorporated in a gas heated oven with equal results. In other words, the method of heating the oven cooking cavity is not critical in the practice of the present invention. For the sake of simplicity, oven support racks are not shown in the cooking cavity, but it should be understood that metal racks of welded wire construction would be furnished for the oven and they would be supported on support ladders (not shown) arranged on the opposite side walls 17 and 18, or alternately on rack supporting embossments or ledges.

In the preferred embodiment of the present invention, the entire oven liner 13 would be formed of embossed sheet metal that has a pebbled surface 27 as is best seen in FIG. 2. Such a surface may also be described as being hammered, crinkled, contoured or textured without having sharp edges or deep crevices. Looking at the enlarged cross sectional view of FIG. 3, the spacing between adjacent ridges would be about one-half inch, while the spacing in the transverse direction in FIG. 4 would be about three-fourths inch. These dimensions are not absoultely critical, but they do give some idea as to the actual size of the embossments of plates and oven liners that have satisfactorily performed as described herein.

The present assignee has an earlier patent of Bohdan Hurko, U.S. Pat. No. 3,113,200, which has an embossed bottom wall of the oven liner, but it was for an entirely different purpose; namely, to form a plurality of shallow recesses or pools for collecting food soil for ease in pyrolytic cleaning at oven temperatures above normal cooking temperatures in the heat-cleaning temperature range of between 750 and 950F. See this Hurko patent,Column 3, lines 22-28, for a picture of the Hurko embossments. It is felt that the present invention is easily distinguishable from the invention of this prior I-Iurko U.S. Pat. No. 3,113,200.

Another patent owned by the present assignee in the oven cooking art with an embossed or pebbled surface for the bottom wall of the oven is U.S. Pat. No. 2,718,854 of Harold Michaelis. This Michaelis patent relates to a commercial baking oven using a sheet metal deck 20 of low thermal mass as a replacement for the ceramic tile deck with large thermal mass of the prior art. Such ceramic tile has a comparatively rough surface and relatively poor heat conduction so as to be effective in eliminating burned spots in food baked in warped pans which may make contact with the deck at one or more small areas. Thus, the embossed sheet metal surface of the deck was designed to be in direct contact with the baking pan and to have a low heat transfer rate similar to that of ceramic tiles. In the present invention the embossed sheet metal walls of the oven liner are not designed to be in direct contact with the cooking or baking pan and, therefore, the relative natures of the two inventions are not coextensive.

While I have elected to describe my invention with relation to an embossed oven liner 13, it will readily be apparent to those skilled in this art that the invention may be used on individual panels that cover important areas of the oven liner such as a removable bottom panel and removable vertical panels for the two opposite side walls and the rear wall of the oven liner.

The embossed metal substrate 27 is illustrated as a pebbled surface, but it may also be described and include such other surfaces as hammered, textured, contoured and crinkled, it being understood that the surface should contain no sharp edges or deep crevices.

Applied over the embossed metal substrate 27 is a thin layer of vitreous porcelain enamel 29 which has a porous matte surface texture deposited thereon for the purpose of oxidizing at normal cooking temperatures the accumulation of carbonaceous residue which forms on the walls of the oven liner during most cooking operations. Such a porcelain enamel finish may be of the type as defined in the U.S. Pat. No. 3,580,733 of Robert Ott which is assigned to the SCM Corp. of Cleveland, Ohio. This dark-appearing layer 29 can best be described as resembling a porcelain blotter. This coating is composed of rather large granules that are loosely fused to form a very porous refractory type coating. This vitreous enamel layer 29 is applied nonuniformly in such a way as to allow an extra thickness of the coating material to accumulate in the valleys be tween the ridges thereby increasing the porcelain blotter capability. Such a double thickness is shown in FIGS. 3 and 4 as highlighted by reference numeral 31. While this invention might be a little difficult to fully appreciate when illustrated in a pen and ink patent drawing, it is much easier to recognize from a full-size working model of the invention. One of the things that an embossed texture or pebbled surface does is to break up the line of sight and reduce the specular reflectance of the wall surface so that it requires six to eight heavy applications of food soil to the surface before any staining of the porcelain enamel coating is noticeable. For example, the surface contour as illustrated in FIG. 2 has a 21 per cent increase in surface area over a flat plate due to the textured design of the surface. This represents a 21 per cent increase in the continuous cleaning coating 29 on the same projected area. Since these coatings function as porcelain blotters, there would be a 21 per cent increase in volume in the same area to absorb food soiling.

The continuous clean coating 29 when applied over the embossed metal substrate 27 takes more material than would be required by a nominal increase of 21 per cent of surface area. The amount of increase of the coating material appears to be close to about 35 per cent. This additional amount of coating is attributed to the leveling effect of the coating. It tends to retain the same thickness on the ridges, but fills the valleys deeper than would be obtained on a flat surface. Again, this increase in bed depth also. increases the porcelain blotter capability. The carbonaceous residue, such as food soil and grease spatter, also appears to flow by capillary condensation from the ridges to the valleys, thus making the porcelain blotter effect even more effective.

The improved results obtainable by the use of the present invention were totally unexpected when this design was originally proposed for evaluation. It is our considered opinion that the use of the present invention provides a cleaner looking oven wall surface with a continuous clean coating than any such surface of competing designs which are available on the market that we have evaluated, bar none.

Modifications of this invention will occur to those skilled in this art, therefore, it is to be understood that this invention is not limited to the particular embodiments disclosed, but that it is intended to cover all modifications which are within the true spirit and scope of this invention as claimed.

What is claimed as new and desired to be secured by Letters Patent of the UnitedStates is:

l. A cooking apparatus comprising an oven cavity formed by a box-like metallic oven liner and a frontopening access door, heating means supplied to heat the cavity for normal cooking operations, at least the bottom wall of the oven liner being embossed with a surface grain of pebbly appearance to create a natural pattern of shadows on the surface and reduce specular reflection therefrom, and (having a pebbled surface with) a layer of vitreous porcelain enamel having a porous matte surface deposited thereon so as to oxidize the accumulation of carbonaceous residue which forms during most cooking operations.

2. A baking oven having metallic walls forming an oven cooking cavity, and heating means furnished with the oven for raising the oven air temperature to about 550F. for normal cooking operations, at least the bottom wall of the cooking cavity being embossed with a surface grain of pebbly appearance to create a natural pattern of shadows on the surface and reduce specular reflection therefrom, and (having a pebbled surface texture with) a top coating of vitreous porcelain enamel having a porous dark matte surface deposited thereon to establish a continuous cleaning action during normal cooking operations of food soils and grease spatters which accumulate during most cooking operations.

3. A cooking oven having metallic walls forming an oven cooking cavity, at least one wall including a door for gaining access thereto, heating means furnished with the oven for raising the oven air temperature through a cooking temperature range between about 150 and 550F., the bottom wall and at least some of the vertical walls of the oven cooking cavity being embossed to have no sharp edges or deep crevices, said embossed surfaces being coated with a layer of vitreous porcelain enamel having a porous dark matte finish to create a continuous cleaning action during normal cooking operations for removing accumulated food soils and grease spatters,

4. A baking or broiling oven having metallic walls forming an oven cooking cavity, and heating means furnished with the oven for raising the temperature of the said walls to a normal cooking temperature range somewhere between about 150F. and 550F., at least the bottom wall being formed with a hammered pattern comprising a generally uniform array of alternate convex and concave formations with no sharp edges or deep crevices, and a top coating of vitreous porcelain enamel on the hammered pattern, said coating having a porous dark matte finish to establish a continuous cleaning action during normal cooking operations of food soils and grease spatters which accumulate on the hammered pattern during cooking.

5. A baking or broiling oven as recited in claim 4 wherein the said hammered pattern is a pebbled surface that is predominantly of a plurality of domed or convex formations with narrow valleys inbetween, said porcelain enamel coating being thicker in the valleys than on the convex formations whereby this increased coating depth serves to increase the porcelain blotter capability in the area where the soil accumulates the most.

6. A cooking oven having metallic walls forming an oven cooking cavity, and heating means furnished with the oven for raising the temperature of said walls to a normal cooking temperature range somewhere between about l50 and 550F., the bottom wall and at least three vertical walls forming the oven cavity being of textured metal with a pebbled, hammered, contoured or crinkled finish without sharp edges or deep crevices to have a surface grain of pebbly appearance to create a natural pattern of shadows on the surface and reduce specular reflection therefrom, and a layer of vitreous porcelain enamel adhering to the exposed surface of the textured metal and having the continuous cleaning property at normal cooking temperatures of diminishing the accumulation of carbonaceous residue which results from the exposure to grease spatters.

7. A cooking oven as recited in claim 6 wherein the said layer of vitreous porcelain enamel is of dark porous matte texture, said layer being thicker in the valleys than on the raised (embossed) portions of the textured metal thereby increasing the porcelain blotter capability in the area where the soil accumulates the l'llOSt.

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1. A cooking apparatus comprising an oven cavity formed by a box-like metallic oven liner and a front-opening access door, heating means supplied to heat the cavity for normal cooking operations, at least the bottom wall of the oven liner being embossed with a surface grain of pebbly appearance to create a natural pattern of shadows on the surface and reduce specular reflection therefrom, and (having a pebbled surface with) a layer of vitreous porcelain enamel having a porous matte surface deposited thereon so as to oxidize the accumulation of carbonaceous residue which forms during most cooking operations.
 2. A baking oven having metallic walls forming an oven cooking cavity, and heating means furnished with the oven for raising the oven air temperature to about 550*F. for normal cooking operations, at least the bottom wall of the cooking cavity being embossed with a surface grain of pebbly appearance to create a natural pattern of shadows on the surface and reduce specular reflection therefrom, and (having a pebbled surface texture with) a top coating of vitreous porcelain enamel having a porous dark matte surface deposited thereon to establish a continuous cleaning action during normal cooking operations of food soils and grease spatters which accumulate during most cooking operations.
 3. A cooking oven having metallic walls forming an oven cooking cavity, at least one wall including a door for gaining access thereto, heating means furnished with the oven for raising the oven air temperature through a cooking temperature range between about 150* and 550*F., the bottom wall and at least some of the vertical walls of the oven cooking cavity being embossed to have no sharp edges or deep crevices, said embossed surfaces being coated with a layer of vitreous porcelain enamel having a porous dark matte finish to create a continuous cleaning action during normal cooking operations for removing accumulated food soils and grease spatters.
 4. A baking or broiling oven having metallic walls forming an oven cooking cavity, and heating means furnished with the oven for raising the temperature of the said walls to a normal cooking temperature range somewhere between about 150*F. and 550*F., at least the bottom wall being formed with a hammered pattern comprising a generally uniform array of alternate convex and concave formations with no sharp edges or deep crevices, and a top coating of vitreous porcelain enamel on the hammered pattern, said coating having a porous dark matte finish to establish a continuous cleaning action during normal cooking operations of food soils and grease spatters which accumulate on the hammered pattern during cooking.
 5. A baking or broiling oven as recited in claim 4 wherein the said hammered pattern is a pebbled surface that is predominantly of a plurality of domed or convex formations with narrow valleys inbetween, said porcelain enamel coating being thicker in the valleys than on the convex formations whereby this increased coating depth serves to increase the porcelain blotter capability in the area where the soil accumulates the most.
 6. A cooking oven having metallic walls forming an oven cooking cavity, and heating means furnished with the oven for raising the temperature of said walls to a normal cooking temperature range somewhere between about 150* and 550*F., the bottom wall and at least three vertical walls forming the oven cavity being of textured metal with a pebbled, hammered, contoured or crinkled finish without sharp edges or deep crevices to have a surface grain of pebbly appearance to create a natural pattern of shadows on the surface and reduce specular reflection therefrom, and a layer of vitreous porcelain enamel adhering to the exposed surface of the textured metal and having the continuous cleaning property at normal cooking temperatures of diminishing the accumulation of carbonaceous residue which results from the exposure to grease spatters.
 7. A cooking oven as recited in claim 6 wherein the said layer of vitreous porcelain enamel is of dark porous matte texture, said layer being thicker in the valleys than on the raised (embossed) portions of the textured metal thereby increasing the porcelain blotter capability in the area where the soil accumulates the most. 